Sorry, I wish I could help you but I do not use the QL17 GN feature because it is not as good as the Nikkor 45mm f/2.8 GN lens or the guide number feature of the Minolta Hi-Matic 9. The two main things I do not like are:

1. The QL17 has only 3 guide number settings (metric 14, 20, and 28).

2. The QL17 guide number feature does not function unless the camera is loaded with functioning batteries.

Please let me know if you find an answer to your question.